I was checking the content of a Springer journal, when I found out some papers which are not open access, yet they are made public and everyone can download them. While other articles, also published in subscription mode, do not have the option of being downloaded.

My question is why some articles have the option of being public and downloaded even when they are not open access, while some other articles don't.

To illustrate what I'm talking about, I give the following two articles

Article published in subscription mode, yet it is public and can be downloaded by anyone

Article published in subscription mode, yet it is not public and cannot be downloaded by anyone

Is there a reasonable explanation?